Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Modeling negative capacitance effect in organic polymers

Abstract: We have developed an extension of the Drude model for oscillators to determine capacitance in organic polymers. The extension covers the effect of time delay caused by dispersion in the carrier transport. This was done using a complex mobility parameter. Negative capacitance effect could be observed in simulation at low frequencies provided that model parameters are appropriately chosen. In matching the simulation results to a set of data reported [Phys. Rev. B. 63 (2001) 125328] we have computed very reasonable values of the transport parameters in regimes where either positive capacitance or negative capacitance is dominant. Negative capacitance effect was attributed to charge trapping in a dispersive media when the carrier mobility had a negative imaginary component. Qualitative agreement was achieved to first order between simulation and observation provided that a mild frequency dependence exists in the carrier mobility. We believe our model is a better approach to extract transport parameters from capacitance–frequency curves when detailed conduction processes could not be easily identified such as in an environment of disordered complex molecules.

Protection of electrical power supply systems

Abstract: An electrical power fault protection relay operates when the calculated impedance of the section of the system it protects shows a sudden change. The instantaneous voltage and current is measured. A calculation device then calculates the Fourier transform of a window of the actual voltage and current over a time interval and of the modified current that would flow if the voltage on each side of the time interval was zero. The actual impedance is calculated from the ratio of the Fourier transforms of the actual voltage and the modified current.

Dual coupled inductor fed isolated boost converter for low input voltage applications

Abstract: A new isolated boost DC-to-DC converter suitable for low input voltage application is proposed. It features low switch current stresses, a wide input voltage range, and inherent inrush current protection, essential for the design of a low-to-high voltage conversion circuits. A comparative analysis and experimental results are presented to demonstrate the validity of the proposed converter.

Electronic Temperature Compensation of Lateral Bulk Acoustic Resonator Reference Oscillators Using Enhanced Series Tuning Technique

Abstract: This paper reports on the demonstration of series tuning for lateral micromechanical oscillators and its application for electronic temperature compensation of piezoelectric lateral bulk acoustic resonator (LBAR) micromechanical oscillators. Two aluminum nitride-on-silicon (AlN-on-Si) piezoelectric LBARs, one operating at 427 MHz (Rm ≈180 Ω, Qunloaded ≈ 1400) and the other operating at 541 MHz (Rm ≈ 55 Ω, Qunloaded ≈ 3000) are interfaced with a 13 mW three-stage tunable TIA implemented in 0.18 μm 1P6M CMOS process to sustain the oscillation. Recognizing the impact on the frequency tuning range due to the body capacitances appearing in parallel with the ports of the resonator, the TIA uses parasitic cancellation techniques to neutralize this effect and boost the tuning range of 427 MHz and 541 MHz oscillators, by as much as 12× to 810 ppm and 1,530 ppm, respectively, with negligible impact on the phase noise performance. The shunt parasitic capacitor is either resonated out with an active inductor or is cancelled out by using a single-terminal negative capacitor of equal value. However, the oscillator that uses negative capacitance parasitic cancellation yields larger tuning. This extended tuning range is used for temperature compensation. A 2 mW bandgap-based temperature compensation circuit which uses second-order parabolic approximation is fabricated on the same chip. Using this temperature compensation circuit has lowered the overall frequency drift of a 427 MHz tunable oscillator using negative capacitance cancellation from ±390 ppm to ±35 ppm in the -10°C to 70°C temperature range. The phase noise of this oscillator reaches -82 dBc/Hz at 1 kHz offset. The total phase noise variation for offset frequencies below 10 kHz is under 5 dB within the specified tuning range, and the best phase noise floor is under -147 dBc/Hz . Due to the higher Q and lower insertion loss of the resonating tank, the 541 MHz oscillator achieves -86 dBc/Hz at 1 kHz offset, and lower phase noise floor of -158 dBc/Hz.

A single-phase bidirectional dual active half-bridge converter

Abstract: A bidirecitonal dual active converter with the power factor control capability is proposed for low-power on-board battery charger application. The source side half-bridge acts as a pulse-width modulation (PWM) converter that maintains the unity power factor. The battery side half-bridge converter acts as a dual active bridge (DAB) together shares the same DC link voltage with the PWM converter. Asymmetric duty cycle technique in which turn-on and -off time duration of primary switches in DAB converter are changed to control the charges of two capacitors is employed to eliminate imbalance voltage phenomenon. Thus, the input current can shape in phase with the voltage source and promising high efficiency of PWM converter. Simulation and experimental results are included to verify theoretical analysis.